1096539 - Celery reconnect support

https://bugzilla.redhat.com/show_bug.cgi?id=1096539

This commit allows celery to recover from ConnectionError exceptions experienced when connecting to qpidd. This provides graceful recovery if you are already connected to qpidd and qpidd shuts off unexpectedly, and comes back. Qpidd can stay off for any length of time, and celery will "hold". Once qpidd comes back online, celery will recover. This "hold" behavior is also present on initial connection, which should finally allow you to start celery services in any order with respect to Qpidd.

Special care has been taken to still allow authentication failures to exit with a full traceback, as those won't benefit from "retry" functionality. It's kind of a hack, but related to qpid.messaging raising a ConnectionError when it should be raising an AuthenticationFailure. See the docblocks for more on this.